Give yourself a manicure and pedicure every week.

I know what you're thinking.  "How girly!  What does that have to do with health?" or "I'm a man; men don't get manicures," but don't stop reading yet.  You would be surprised by the number of germs lurking in the cracks of your nails.  You would also be surprised by the horrible infections you can get from germs getting into torn cuticles.  Making sure your nails are trimmed and filed and that your cuticles are in good shape can reduce the potential for some nasty infections, and nicely groomed nails make you look "put together" whether you are a man or a woman.  It's also helpful if you are a nail biter.  It's amazing how many germs get into your body when you're a nail biter.  If you go through the trouble of taking care of your nails each week, you are much less likely to bite your nails and, thus, less likely to introduce germs into your body via the nail biting process.  It's easy to give yourself a manicure / pedicure, cheaper than going to a professional, and probably safer to do it at home with your own equipment (which you know is sanitized because you sterilized those tools yourself) instead of going to a place where each tool may be used on hundreds of other people (a great way to transmit germs).

How to do a manicure / pedicure:

1. If you wear nail polish remove it.
2. Wash your hands and feet and clean out all the grime underneath your nails using a nail brush or by scratching a bar of soap with your nails and working it out.
3. Apply cream to your hands, feet, nails, and cuticles to moisturize them.  (This will make it easier to work with your cuticles and reduce cracking and splitting of both nails and skin.)
4. Make sure all of your equipment is sterile (otherwise you may actually introduce more germs to the area).  I soak mine in alcohol or at least rub them down with alcohol.
5. Clip your nails using a nail clipper (not scissors) to their desired length and shape.  Make sure you don't cut them back too short because it can be painful and even expose delicate layers of skin which could actually cause infection.  Also be careful not to trim back the corners too much or you could end up with an ingrown nail.  Your best bet is to cut them straight across (you can round the edges when you file).
6. Using a nail file or emery board, file your nails into their desired shape and get rid of rough edges.  (Make sure you move your file in one direction.  Going back and forth could create tiny splits your nails.)
7. Now it's time to take care of those cuticles.  If they're really tough, you may need to soak them for awhile to soften them up (bring out the foot spa) and reapply the moisturizer.  
8. If you have any cuticles with hang nails, pieces of dead hanging skin around your nail (which most people end up ripping off and creating painful, bleeding tears), cut them off making sure that you don't actually cut into living skin (just go for the dried up dead stuff).  Some people use a specially designed cuticle cutter, but I just use my nail clippers.  
9. Next you need to push your cuticles back, which will help reduce hang nails in the future.  Some people use their fingers to push them back while others use store-bought cuticle sticks.  Just remember that whatever you use, it shouldn't be sharp because sharp objects could cut your cuticles (creating yet another place for infection) and can scratch your nails (which is just more unsightly than anything else).
10. While you're at it, you may want to use a pumice stone to get rid of any unwanted calluses or ultra rough patches of skin (especially on your feet).
11. If you want a nice, soft gloss to your nails, buff them.  Wipe off any excess moisturizer (and dry thoroughly if you soaked your cuticles), get out your buffer, and buff the top of your nails in one direction, but don't do it more than a couple times a week because each time you buff your nails, they get thinner, and you don't want thin brittle nails.
12. If you want to polish your nails, go for it.  (Since I'm not focusing on the cosmetic aspect manicures and pedicures, I won't get into the details of the perfect nail polishing technique.)
13. Poof!  You've just given yourself a manicure / pedicure.